The invention relates generally to communication systems, and more particularly a method and apparatus for connection format conversion in communication systems.
Communication between a calling party and a called party may be established over a communication network. Such a communication network may include a plurality of network switches that transport data in one of a variety of data transport protocols. Asynchronous transfer mode (ATM) technology is becoming the technology of choice for such broadband data communications. Within such ATM systems, a number of different service categories exist to facilitate the needs of different users.
Service categories supported by ATM can be grouped into real-time and non-real-time service categories. Real-time service categories include constant bit rate (CBR) and real-time variable bit rate (rt-VBR). Non-real-time service categories including non-real-time variable bit rate (nrt-VBR), available bit rate (ABR), and unspecified bit rate (UBR). Each of these different service categories includes a set of parameters that characterize the traffic contract that controls transmission of data within the data communications network. These parameters define the quality of service (QoS) for each given connection within the ATM network.
Nrt-VBR can be characterized as a bandwidth-on-demand (BOD) service category that tends to be used in non-real-time applications that are xe2x80x9cburstyxe2x80x9d in nature, where xe2x80x9cburstyxe2x80x9d indicates that the data is often transmitted in short, concentrated, bursts. These types of connections typically require a committed cell loss ratio (CLR), which is expected to remain constant during the existence of the connection. The UBR service category is typically associated with non-real-time applications that have no service guarantee required by the ATM network. UBR is typically associated with a BOD type of connection that uses the leftover bandwidth in the network once all other service categories have consumed their bandwidth requirements.
When connections are established for UBR and nrt-VBR service categories, the characteristics of the connection are often dependent on available resources within the network at that particular time. In many cases, the available resources in the network change during the existence of the connection. However, once a UBR or nrt-VBR connection is established, the parameters that describe the data carrying capacity of the connection cannot be altered unless the connection is terminated and reestablished. This can lead to inefficient use of network resources, as additional bandwidth carrying capability may be present but not utilized because of the lack of feedback in UBR and nrt-VBR connections.
Therefore, a need exists for a method and apparatus that allows for nrt-VBR and UBR connections to be provided with the means to adjust data transmission rates based on current network characteristics.